Sensor nodes in WSN play a vital role in communication, IoTs and many other emergencies too. However, the energy consumption of nodes is a major setback to these, which incites various malicious nodes/attacks. This article studies and presents the solution to Vampire attack-one of those kinds of attacks. It depletes the energy by route elongation of data transmission. This article has suggested a novel two-fold mechanism to detect the attack by integrating co-operation trust mechanism and the mitigation of the attack by selecting the secure route by policy gradient-deep reinforcement learning. The designed protocol also ensures the selection of a secure hop even in the presence of the vampire attack. The results are compared with various other existing state-of-the-art schemes and have improved the detection ratio by 20% compared to the forecasting methods applied for detecting the vampire node's behavior. The network lifetime has also improved by 3% than the benchmark dynamic source routing.